Refuse disposal



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United States Patent 3,289,617 REFUSE DISPOSAL Frank S. Simpson, Alton, Ill., assignor to Illinois Stoker Company, Alton, 11]., a corporation of Delaware Filed Aug. 12, 1963, Ser. No. 301,401 1 Claim. (Cl. 1 7) This invention relates generally to refuse disposal, and particularly to the agitation in an incinerator of bodies having such compaction, moisture content, or other condition which inhibits their combustion in the normal way.

Endless traveling grates, variously known in the art as chain grates, oscillating grates, vibratory grates, or moving grates, have long been used in stokers for boilers, and other situations where the generation of usable heat is sought, but more recently they have found extensive application in giant incinerators used by municipalities for the purpose of disposing of large volumes of refuse. Regardless of the purpose of the furnace in which such a traveling grate is used, it is customary to deposit the fuel, or other material to be burned, upon the upper flight of an endless traveling grate near one end thereof; to carry out the combustion substantially from end to end of the upper flight, and to discharge the ash or residue at the opposite end. Such a traveling grate is frequently provided with means for forcing a draft of air through those portions of the grate on which the combustion takes place, and the grate structure is usually sufiiciently open (as distinct from imperforate) to permit the passage of air (to support combustion) through it. The forced draft is provided by any suitable means, such as a fan or blower, capable of developing pressure sufficient to maintain a steady flow of air to a series of locations beneath the upper flight of the grate, or those portions thereof at which combustion takes place. Pressure of less than five inches hydrostatic head (at the exhaust of the blower) is ade quate for that purpose, and is conventional.

In a stoker used for the production of usable heat, the traveling grate carries a relatively thin bed of solid fuel through the furnace, and preferably maintains the fuel bed quiescent. On the other hand, the traveling grate in an incinerator carries a relatively thick bed of refuse, some of which may be garbage, water-soaked paper, or books, mail order catalogs, magazines, or the like, which, even while relatively dry, resist combustion. In such an incinerator, used for municipal refuse disposal, the bed of material on the traveling grate may be in the neighborhood of four or five feet deep.

In view of the content of difiicultly combustible material in municipal collections of refuse, it is frequently necessary to agitate the bed of material on the traveling grate in order to avoid the presence, in the residue discharged from the grate, of large volumes of unburned, but Heretofore, such agitation has been accomplished by inserting 'pokers through openings in the furnace walls, and manually manipulating them to stir up the bed of burning refuse on the grate. The object of the present invention, generally stated, is to provide a method of, and apparatus for, facilitating the incineration of difficultly combustible materials in refuse, and reducing the content of unburned combustible material in the ash or residue discharged by the incinerator.

A more specific object of the invention is to provide a method of agitating a bed of refuse, as it moves through an incinerator, in a manner which is more convenient and etficient, and less laborious than that heretofore employed.

Another object of the invention is to provide a method and apparatus whereby to increase the capacity of an incinerator of the character referred to.

The invention contemplates, generally, that the burnburning refuse.

Patented Dec. 6, 1966 ing bed of refuse on the traveling grate of an incinerator be agitated by the injection of air, or other gas, through the grate, and under pressure sufficient to locally lift, expand and fluff matted, wet, or otherwise compacted, components of the refuse bed. While ordinarily such injection at a distance of a foot or so lengthwise of the travel of the burning bed will sufiice where the refuse is extraordinarily high in content of magazines, catalogs, books, or other comparable matted material, it may be desirable to provide a plurality of such gas injection stations, preferably spaced apart a substantial distance.

The invention involves the use of a conventional traveling grate arranged to move the bed of burning refuse substantially horizontally, and, as is customary in such incinerators, the grate has about ten percent of its bed sustaining a surface area open to permit the passage of air to support the combustion. Structurally speaking, the present invention adds to the conventional structure a means for injecting air, or other gas, under relatively high pressure, upwardly through the grate beneath the bed of The magnitude of the pressure 0n the injected air is substantially in excess of that heretofore applied to force a draft through the openings in the grate; and must be sufficient to overcome, or locally lift, the dead weight of the affected increments of refuse on the grate. For example, in the design of municipal incinerators, the value of twenty-two pounds per foot of depth per square foot of grate is the commonly accepted standard which provides a reasonable factor of safety; and since such incinerators are seldom designed to carry a bed whose average depth is less than two feet or more than five feet, a suitable pressure on the injected air is between twelve and thirty inches of water. The deeper the bed of refuse, the higher the required pressure on the injected air. Indeed, higher pressure is preferred because, consistent with economy of operation, it does no harm, but does permit of intermittent operation, and hence conserves the energy consumed in so injecting the air when the burning refuse bed does not require it.

There is another reason for preferring higher pressure on the injected air. Because the openings through the grate occupy only a fraction (usually ten percent) of the the grate area, if, at start up, there is matted refuse which hermetically seals those grate openings (which, at the moment, are positioned so as to be exposed to high pressure), then the force applied to the bed, and tending to lift it, is only ten percent of that which would be attained if the grate openings were not completely sealed. While such a situation seldom occurs in practice, and when it does occur, it cannot for long endure (because of the heterogeneity of refuse); it is nevertheless better to be prepared to meet the emergency than to regret the unpreparedness.

An illustrative example of one form of apparatus for carrying out the invention is shown in the accompanying drawings, in which the form of traveling grate is that known in the art as the link and pin type, but it will be understood that other grate constructions, such as that known as the bar and key type, are equally applicable to the present invention. In the drawings:

FIGURE 1 is a diagrammatic view in side elevation of a typical incenerator to which the invention is applied;

FIGURE 2 is a partial top plan view of a portion of an incenerator structure (without traveling grate) and illustrating one form of apparatus usable in connection with the present invention;

FIGURE 3 is a view in elevation at the lower side of FIGURE 2 with a conventional traveling grate added;

FIGURE 4 is a sectional view taken along line 44 of FIGURE 3;

FIGURE 5 is a partial bottom plan view of the portion of traveling grate shown in FIGURE 3;

FIGURE 6 is a view in side elevation of a typical link in the traveling grate;

FIGURE 7 is a top plan view of a side link in the traveling grate;

FIGURE 8 is a top plan view of a wear link in the traveling grate;

FIGURE 9 is a top plan view of a drive link in the traveling grate;

FIGURE 10 is a top plan view of a regular link in the traveling grate; and

FIGURE 11 is a diagrammatic view depicting the manner in which the bed of refuse is agitated in accordance with the present invention.

An incinerator of the type herein referred to is illus trated schematically in FIGURE 1, and consists of a receiving hopper 1 having a chute 2 leading to an inclined conveyor 3 on which some preliminary drying of the refuse deposited in the hopper 1 takes place. The lower end of conveyor 3 overlies the upper flight 4 of a traveling grate, and hence refuse is discharged by conveyor 3 onto the upper flight 4. Between the upper flight 4 and the lower flight of the traveling grate, a series of wind boxes 6 is provided. Air to support combustion of the refuse bed on the upper flight 4 is introduced through wind boxes 6. The present invention contemplates that at least one of the conventional wind boxes, such as that shown at 7, be converted for the handling of high pressure air and the injection of it through the grate and beneath the bed of refuse immediately thereabove. Combustion occurs on the upper flight 4 of the traveling grate, and the residue or ash is discharged over end 8 thereof. The entire organization is enclosed in suitable walls 9, and provided with a stack 10.

Referring now to FIGURES 2, 3 and 4 of the drawings, there is illustrated the portion of the incinerator structure which occupies position 7 in FIGURE 1, together with its accessory equipment. On the outside of side wall 9, there is a suitable blower 11, capable of delivering air at a pressure on the order of twelve to thirty inches of water. From the blower 11, a duct 12 conveys the high pressure air to a tuyere 13 which extends entirely across the traveling grate widthwise thereof, and is provided with a series of throats 14 extending upwardly to a position at the level of the bottom surface of upper flight 4 of the traveling grate. The open top of each of throats 14 is surrounded by a plate 15 having a central opening 16 of slightly less dimension than the upper end of throat 14. At each end (in the direction of travel of the grate) of plate 15, there is provided an auxiliary plate 17 for guiding the traveling grate onto and off of plate 15.

From blower 11 through duct 12, tuyere 13 and throats 14, the stream of high pressure air is delivered to the lower surface of upper flight 4 of the traveling grate. From the opening in plate 15, the high pressure air is injected through the openings between the links of the traveling grate which, as stated hereinbefore, constitute about ten percent of the total surface area of the traveling grate. The portions of plate 15 about opening 16 provide a substantial seal with the lower surfaces of the grate links, and thus largely eliminate leakage of the high pressure air sidewise and endwise. To minimize such leakage, it is desirable to effect, about the boundaries of openings 16, as good a seal as is obtainable consistent with other operating conditions.

Between the several throats 14, there is provided a series of parallel supporting members running lengthwise of the traveling grate. These supporting members include side sills 18 and carry bars 19. The side sills are supported on walls 9, while the carry bars are supported by cross-runners 20 located at each side of the several wind boxes 6 and of the tuyere 13.

As previously indicated, in the form shown in the drawings, the traveling grate is of the link and pin type, and, as clearly shown in FIGURE 5, includes four different styles of links. There are side links 21 at the outer margins of the grate. There are lefthand drive links 22 and righthand drive links 23 at opposite sides of rollers 24. There are righthand regular links 25 and lefthand regular links 26. And there are wear links 27 which ride upon the carry bars 19. At each end of the several links, a pin 28 passes therethrough to connect them together. The rollers 24 are for engagement with the drive sprocket.

Insofar as the present invention is concerned, the several styles of link may be identical in side elevation, but FIGURE 6 represents the side elevation of the side and wear links. The latter have bottom flanges 29 which the regular links and drive links do not have. The righthand and lefthand links of the same style are mirror images of each other. However, the several links differ in both bottom and top plan view, as shown by FIGURES 7 through 10 in contrast with FIGURE 5. The top flange of each link of all types is provided at one side thereof with at least one indentation which forms nearly half of openings 30 throughout the grate. Such indentations are shown in FIGURE 7 at 31, in FIGURE 8 at 32, in FIGURE 9 at 33, and in FIGURE 10 at 34. The openings 30 formed by one or two of the several indentations, together with the clearance between links both endwise and sidewise, leaves an open area amounting to approximately ten percent of the top surface area of the grate.

The operation of the method and apparatus is illustrated in FIGURE 11, where the bed of refuse is four or five feet deep on the flight 4 of the traveling grate, and is burning before a given increment reaches a position above throat 14. Assuming, at Worst, an instantaneous condition (seldom, if ever, encountered in practice) such that all of openings 30 (which are momentarily positioned over the openings 16) are sealed by overlying compacted material with an overburden amounting to pounds per square foot and that the only area upon which the air pressure can act is the ten percent open area in the grate (provided by openings 30 and clearance), it is apparent that the force required to locally budge an increment of refuse which is sealing the openings 30 is more than 100 pounds times the area (in square feet) which is exposed to the action of the high pressure air. Now in a practical example, the area of a single opening 30 (formed by two complementary indentations, such as 29 and 34, with intervening clearances) is approximately 1.75 square inches which, at a pressure of thirty inches of water, yields force of approximately two pounds per opening, and hence substantially exceeds the weight tending to maintain the opening closed (i.e.,

IOU/144x 1.75:1.21 pounds) Indeed, theoretically, a pressure of nineteen inches of water should budge it. However, once the overburden tending to seal an opening is budged, and the high pressure air permitted to pass through the opening, the area upon which the pressure can act is multiplied and the local lifting extended until the bubble bursts, which is the condition illustrated at 41 in FIGURE 11.

The conditions more commonly encountered in practice do not involve any such unique combination of circumstances as that related above where all of the grate openings through which the high pressure air can be injected concurrently are sealed. On the contrary, the heterogeneous character of refuse militates against its occurrence, and although some grate openings may at a given instant be sealed, the continued injection of high pressure air through nearby openings will ordinarly, in the course of a few seconds, dislodge that which is sealing another. If the high pressure air injection is commenced at start up and continuously maintained as long as the traveling grate is laden, air pressure on the order of twelve inches of water is usually adequate to keep the refuse bed agitated, periodically bursting, and fluffed. Ordinarily, the most serious condition is encountered on start up after the incinerator has been shut down while laden with wet stuff,

in which event air pressure on the order of fifteen to eighteen inches may be required to start the agitation immediately, but after the grate has traveled far enough to bring freshly deposited refuse into the zone above throats 14, pressure on the order of twelve inches will maintain adequate agitation, with buoyant effect upon the increments of the burning bed which are over or adjacent the zone of throats 14. In the process of being so buoyed, the bed of refuse repeatedly blows apart (as shown at 41 in FIGURE 11), fiuffs up the compaction in the environs of the high pressure air jets, and thereby exposes the previously compacted masses of combustible material for thorough burning.

In addition to eliminating from the residue or ash a substantial volume of unburned combustible material, the invention, in some instances at least, enables the production (i.e., destruction) rate of given incinerator installations to be increased either by traveling at higher speeds than heretofore, or by increasing the depth of the burning bed thereon. Moreover, it is apparent that, if and when desired, the blower 11 may be so constructed and controlled in coordination with the conditions within the furnace or the rate of air flow through the tuyere, that the pressure developed by the blower is automatically varied to take care of changing conditions as they arise, i.e., to increase or decrease the air pressure as needed to effect the required agitation of the burning bed of refuse.

From the foregoing description, those skilled in the art should readily understand the construction of the apparatus and the operation of the method, and appreciate the advantages thereof. While a full disclosure has been given of an embodiment of the invention, such is to be regarded merely as illustrating, and not as limiting, the invention. As indicated hereinbefore, various alternative forms of traveling grate can be used in lieu of the form shown in the drawings, and other modifications and variations will present themselves to those skilled in the art without departing from the spirit of the invention or the principle of its operation, or the scope of the appended claim,

Having thus described the invention, what is claimed and desired to be secured by Letters Patent is:

The method of promoting combustion in refuse burning incinerator furnaces provided with a traveling grate and apertures through the grate to pass air for combustion, which method comprises,

(a) loading on said grate a bed of refuse which is some feet in thickness and which covers said apertures,

(b) moving said bed of refuse by said grate through said furnace where combustion of the refuse takes place,

(c) supplying said bed of refuse while undergoing cornbustion with air to support combustion from tuyeres located below and within a narrow zone along said grate as successive grate apertures open to said tuyeres, and

(d) providing sufficient air pressure to some of said tuyeres that the air passing through apertures aligned therewith produces sufficient force to lift and agitate the refuse locally of said some of said tuyeres and progressively along the grate as it burns.

References fitted by the Examiner UNITED STATES PATENTS 1,505,505 8/1924 Stratton. 2,057,681 10/1936 Harrington -15 2,481,504 9/1949 Ferro et a1 1107 2,894,465 7/1959 Phillips 11069 3,016,849 1/1962 Markle et a1. 11018 FOREIGN PATENTS 161,151 2/1922 Great Britain.

0 JAMES W. l/VESTHAVER, Primary Examiner.

FREDERICK L. MATTESON, In, Examiner.

H. B. RAMEY, Assistant Examiner. 

